Ellipsograph



April 1953 R. AUKSTUOLIS 2,636,272

ELLIPSOGRAPH Filed May 12. 1952 Hal.

R LE

F6. 8. FI -'4.

JNVENTOR.

RA PULAS A a/($700415 BY 42m- Q 6M ATTOfC VEY Patented Apr. 28, I953 UNITED STATES PATENT OFFICE 1 Claim.

This invention relates generally to the field of drafting instruments and more particularly to improved forms of such instruments for use in drawing ellipses or other mathematical figures.

Such instruments have heretofore taken a variety of forms including fixed size templates as well as compass-like tools for tracing figures over a wide range of sizes. The template type ellipsographs all possess the basic disadvantage of being only useful for the exact sizes for which templates are available while the latter, or compass-like ellipsographs, which is the general field into which this invention falls, have hereto fore sufiered from a lack of mathematical accuracy and consequently they failed to describe true projections over a range of sizes.

It is an object of this invention to provide a device of the compass-like type that will draw mathematically accurate projections of a given figure. A further object is to provide a device of the type described that will draw such figures. over a wide range of sizes including every size within such range.

These and possibly other objects are attained by providing a device of the type described having a vertical first leg with a centerpoint as well as an offset holding point on its lower end, a vertically movable formed plate such as an ellipse mounted on said first leg above its lower end, means for holding such formed plate in position on said leg, a rotatable and vertically movable sleeve mounted on said first leg above said formed plate, a second leg having drawing means on its lower end and having its other end hinged to said sleeve so that said second leg moves and rotates with said sleeve while being adjustable to any degree of inclination from the longitudinal axis of said first leg, and tension means for holding the second leg against the periphery of the formed plate of the first leg, whereby when said sleeve is rotated about the first leg the second leg traces the periphery of the formed plate and the projection is transferred to the paper by the drawing means on the second leg. Size variation is attained by changing the vertical position of the formed plate of the first leg.

My ellipsograph derives its accuracy from a particular and critical arrangement of its elements. To that end it may be said that the invention is characterized in that the parts are so arranged that the longitudinal axis of the first leg passes through the center of the formed plate and intersects a straight line traced from the drawing tip of the second leg along the inner edge of such leg. The formed plate may be of any desired shape, such as an ellipse, triangle, or irregular polygons and the like.

When constructed in the foregoing manner the device will trace a substantially perfect projection of the shape represented by the formed plate mounted on the first leg.

In somewhat more detail, my invention revolves about the concept of providing a device of the type described having a vertical first leg with a center point and an offset holding point on its lower end, a formed plate having both a center hollow hub and holding means positioned on the first leg above its lower end, said plate and hub being adapted to snugly and slidably fit over said first leg to be held in place thereon by the holding means, a slidable sleeve rotatably mounted on said first leg above the formed plate, a second leg having a forked end fitting over said sleeve and pivotally mounted thereon whereby said second leg slides and rotates with said sleeve while being adjustable to any degree of inclination from the longitudinal axis of the first leg, said pivot points holding the forked end of the second leg into the sleeve of the first leg being so positioned that a line drawn through said points will pass through the longitudinal axis of the first leg, spring tension means holding the inner edge of the second leg against the periphery of the formed plate mounted on the first leg, and drawing means attached to the other end of the second leg and so positioned that a line drawn from the drawing means tip along the inner edge of the second leg will intersect the longitudinal axis of the first leg at the same point that the line ioining the pivot points of the fork intercept said axis.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by theappended claim rather than by the description preceding them, all changes that fall within the metes and bounds of the'claim; or equivalents of such metes and bounds, are therefore intended to be embraced by the claim.

In the drawings, Figure 1 is a simplified line drawing clearly depicting the critical arrangement of the elements in accordance with the concept of my invention. Figure 2 shows a preferred embodiment of the details shown in Figure 1, while Figure 3 shows a plan view of a type of formed plate adapted for use with my invention. Figure 4 is a plan view of a differently shaped plate adapted for use with this invention.

Figure 1 is a simple line drawing depicting the critical arrangement of the elements of my invention. In Figure l the instrument comprises a fixed vertical first leg l2 having a lower centerpoint [4 and an'offset holding point l5 as well as a top l3. A vertically movable formed plate [6 is mounted on leg l2. A sleeve H is mounted on leg l2 in such a manner that it revolves about leg l2 while being vertically slideable thereon. Attached to sleeve I1 is a movable second leg 20 having a tracing ,tip, 2| and joiningsleeve I! at point 22, this point of juncture at 2 2 is such that the line A-'-B will always pass directly through line CD. To this end, leg 20 may be forked at its upper end so that the forked end pivots on sleeve H at point 22 and itscor responding opposite point, so that lines A-B and -D intersect with each other at-a point on a first fixed vertical leg 252 having an inner edge- 2! I. iounted on leg 242 is a formed plate 2W, said plate being vertically movable and capable of 'being fixed at any desired elevation. Leg 212 is equipped with a center point 2 i l and an ofiset holding point 2E5. Fixed leg 2W. runs through sleeve portion 217 to terminate in holding end 213, the latter being provided with removable cap 213. Sleeve portion 2!! is machined so that it fitsclosely upon leg 25?. to minimize wobble while still permitting sleeve it? to rotate about and slide vertically thereon.

Second leg 22s is provided hinged tosleeve por tion 217 in such a manner that leg 22B rotates with sleeve 2H while being adjustable to any desired degree of inclination from the longitudinal axis of leg 212. It is desirable that the point of intersection of lines AB and C-D also intersects a'line drawn between the points at which forkedend 22M pivots on sleeve 2H. Leg 220 is provided with a drawing tip 22!.

Leg 229 has straight inner edge 238 which'is adapted to glide smoothly over the periphery of formed plate 216 thus to transcribe, via point 22 I, a line tracing of formed plate 2H; into the same surface that supports points 2M, 2 i and 22 i. In order to insure an accurate reproduction of the periphery of plate 2E8, there is provided spring means 223, said spring means comprising a flat spring 223 positioned between the sides of the forked end of leg 228 and with shoulders 22d engaging the outer edges of fork 2253a. The other of s ring 223 is secured to sleeve M? by screws 225; Set screws or other conventional arrangements are provided 101 holding the formed plate and other removable elements in position. The formed plate is thus removable so that it may be exchanged for a difierent plate.

The critical constructional features of my.in-, vention are clearly depicted by lines A-B and CD; point 222, point 22! and point 2| 4, as well as edges 2I6a and 238. It is critical that straight line A--B intersects straight line C-D whenever edge 23s is in contact with edge 215a.

Figure 3 shows an ellipse-shaped formed plate 316 for use in accordance with my invention.

Figure 4 shows an alternate 'shapeotformed plate for use with my invention.

It is to be emphasized that my: invention-re;

quires that a straight lineexten'ded from the drawing tip along the straight inner edge of the second leg will intersect the longitudinal axis of the first leg. Only in this manner will projections of varied sizes be mathematically related to each other.

Where as I have referred enerally to a formed plate, it is to be understood that this invention is limited to tracing thos'e peripheries that progress forward only and do not double back on themselves. In other words, this invention is limited to tracing peripheries that move forwardly at all times from a starting point to return to said starting point.

An inherent and important feature of this invention is the fact that it provides for varying the sizes of the traced projection over a wide range. Thus, to changethe size of the tracing it is only necessary to move the formed plate up or-down on thefixed leg. This feature enables the operator to trace all sizes of projections, from the largest projection when the formed plate is in its uppermost position, to the smallest projection when the formed plate is in its lowermost position on the fixed leg.

Having now described the construction and operation of my invention what I claim and desire to secure by Letters Patent is:

An improved device for drawing projections of given geometric figures, comprising a first leg with a centerpoint as well as an offset holding point on its lower end, said leg being adapted to maintain a vertical position at right angles to a surface contacted by said points, a formed plate mounted on said leg above its lower end, holding means for securing said plate at selected elevation on said leg, a rotatable and slideable sleeve mounted on said leg above the formed plate, a second leg having a forked upper end fitting over said sleeve and being pivotally mounted thereon in such a manner that a line drawn between the pivot points passes through the longitudinal axis of the first leg, said second leg having a straight lower inner edge portion adapted to contact the periphery of the formed plate, drawing means positioned on the lower end of the second leg so that the extension of a line drawn from the drawing tip along the inner edge of said. leg will intersect thelongitudinal axis of the first leg at the same point as that where the line through the pivot points of theiorked end of said second leg intersects the longitudinal axis or" the first leg, and spring tension means for holding the inner edge of the second leg against the periphery of the formed plate, said tension means comprising a fiat springposition'ed between the sides of the forked end of the second leg, one end of said spring having shoulders in contact with the outer edges, or the forked end, and the other end of, said spring being secured to the sleeve mounted on the first leg.

RAPOLAS AUKSTUOLIS.

References Cited in the file of this patent- UNITED STATES PA'IENTS I 

